First, Darren Aronofsky's Black Swan is the finest film I've ever seen in a theater.
Second,this post discusses twist endings of a specific type, so beware of those spoilers.
One of my biggest pet peeves in the genre is the split personality twist. In Psycho, it was original. When I first saw Secret Window, I was blown away by the unexpected shift in the narration, which is a departure from Psycho. But many years and films later, and Secret Window pales. With the likes of Hide and Seek, High Tension, Identity, Fight Club, and Shutter Island all sharing the same territory, I really resent that twist at the end of a movie, especially if it's one I was really immersed in.
To me, the split personality twist is kind of a cop-out. It doesn't have a lot of root in reality, and yet it must be totally accepted on its face. It's too cookie-cutter for me. It doesn't do anything for the plot, generally, but is actually a huge step backwards at the conclusion of the film, where everything you invested in is revealed as immaterial. Therefore, if the director frames the plot like a mystery, and tries to cast suspicion on other characters, it turns out that those characters were acting strangely for no reason at all, and their conduct makes no sense.
And frankly, I'd hate it if I was watching John Wayne or Clint Eastwood get bullied for 90 minutes, and then at high noon he winds up standing in the middle of the street wearing a black hat and white hat stacked on top of one another.
In the split-personality film, there is one re-watch built in, where you find all the clues you missed before, and occassionally huge plot holes. After two viewings, the main value is to watch it with friends and see if they're surprised.
Black Swan manages to use the split personality without falling into any of the holes. And I thought these films were made in one big pit. But this film shows that it's possible to tread around the edges. This is accomplished in one huge way: the very careful disclosure of the split.
Black Swan works the surprise into the plot carefully, so that the film does not end upon the revelation of the split personality. Throughout the film, it is hinted that Portman's character is unstable, using cues, such as the moving face in the mother's painting studio, or the way that the mother does not acknowledge Mila Kunis' presence during the apartment confrontation. Other films often include elements like this, but they are intended to be discovered upon the second watching (for instance, the guard's promise of help to DiCaprio in the opening of Shutter Island). Black Swan cleverly employs the metastructure of Swan Lake to develop the split personality theme with enough directness that the audience should not remain oblivious to the parallel for long. And most importantly, when Portman's psychosis is ascertained, the film does not lose its focus. In a film like Secret Window or High Tension, the narrative revolves around the perspective of the sympathetic main character. Then, when that character goes mad in the third act, the audience must abandon that sympathy and abruptly embrace a different character, who we barely know.
Two alternatives emerge at that juncture. Either the former protagonist, who has gone mad, retains enough charisma to keep the audience's favor, as Johnny Depp was able to in Secret Window, or that character must remain, through a show of suffering and innocence, a sympathetic figure. In accomplishing this, Black Swan keeps the audience balanced between the intensity of experiencing Portman's frightening hallucinations in the first person and the third-person sympathy of watching her unravel.
Another improvement is the presentation of the cause of instability. Other films tend to give a very loose, flimsy reason for why the lead character has gone mad. High Tension: sexual attraction. Secret Window: a breakup. Identity: pre-existing madness. Pre-existing madness may be the worst, since it allows you to build the whole film on one phrase. The others feature ordinary people in ordinary situations, who for some reason suffer extraordinary psychological problems thereafter.
Black Swan devotes the entire film to developing an explanation for Portman's psychosis. This character development lends itself particularly well to film. Other stories that strive to provide a comprehensive backstory to a character often resort to a flimsy explanation scene, where a character details his past, or rely on flashbacks to childhood to pinpoint traumatic or formative experiences. Black Swan works well because the lead character's life is reasonably compressable to what the film reveals. Apparently, Portman's character has been dancing for most of her life, led into that life by her mother, the former ballerina. Her day-to-day has consistently been limited to spending long days with the company, and her nights with her mother. As such, her interaction with others has been primarily limited to the competitiveness and infighting of the dancers, dictated by the militaristic intensity the company and competition for roles, and the overbearing love of her guilt-tripping mother.
As such, Portman's character faces extreme stresses. The natural competitiveness of the ballet is exacerbated by the director, who dabbles haphazardly with the emotions of his dancers. At home, her mother puts out certain expectations while at the same time attempting to downplay those same expectations and remain optimistically realistic. But as many can attest, those do not cancel each other out.
And because her life as played out so rigidly, Portman's character is clearly socially inexperienced, as evidenced by her behavior around Kunis' outgoing character. It follows that she is sexually inexperienced, because she's never really had the time or opportunity to pursue anything of that nature (which is not to say she hasn't been taken advantage of, if we assume that she doesn't lie to the director when he asks about her about the subject). Additionally, ballet tends to postpone puberty in girls by eliminating the requisit body fat that triggers the changes in the body. As such, her repression is physical as well as emotional, creating total volatility. The cause of her psychosis is no mystery, and can credibly be summarized within the span of the film.
As a side note, the film is to some extent an allegory of delayed puberty. The character begins as childlike young woman. Her bedroom demonstrates that she has never abandoned the childhood she was given by her mother to develop an independent personality. Suddenly she becomes two people, nigh-literally. Her moods shift dramatically, she masturbates for the first time (unknowingly in the presence of her mother, no less), she becomes attracted to the older man, begins to have physical encounters, calls her sexuality into question, experiments with drugs and alcohol, and becomes resentful of her mother's best intentions and concerns. Upon everything else, this film highlights how truly bizarre puberty is, especially when taken out of context.
